What you need:
Hot glue gun
Clear plastic tray (cd case)
Red nail polish
Spray Bottle with cold water.
1. Draw your idea on paper and tape it on the inside of the tray.
2. Spray the surface with cold water to prevent the hot glue from getting attached to the plastic .Use the hot glue gun to trace the stencil and let it cool down.
3. Remove it from the plastic and cut away glue strings and mistakes.
Use a thick layer of red nailpolish to paint it (nail polish is thicker and makes it easy to hide the uneven bits) and let it dry. Make two holes on each side and attach to the necklace and voila!